1. Technical Field
The present invention is directed towards a copolymer for use in scale inhibition. More specifically, the present invention discloses an alcohol compatible, water-soluble copolymer that is useful as a corrosion inhibitor.
2. Background Information
In the offshore oil drilling industry umbilical lines are used to transport a variety of fluids over great distances, often tens of kilometers in length. These umbilical lines can consist of several independent lines depending on the type of fluid transported to the reservoir. For example, the fluids can be water-based scale inhibitors used to prevent solid salt formation in the well. Other types of fluid transported include alcohols such as methanol, which can be used to prevent formation of water/methane ice structures downhole. These ice structures can form in the presence of natural gas causing significant problems.
Often the number of fluids transported exceeds the number of umbilical lines available. This can occur, for example, due to a blocked line or the requirement for additional fluid(s) to be transported to the reservoir. Therefore, there is a strong need to be able to combine one or more of the fluids with others in order to address this line constraint. However, a problem can occurs in trying to combine the materials in that they are often not compatible with each other. For example, one of the materials may be water based and not compatible with alcohols transported through the lines, such as methanol. Therefore, there is a need for alcohol compatibility between the chemicals. Further, it would be beneficial if that alcohol compatible chemical also functioned as a scale inhibitor. Such compatibility is very beneficial when an alcohol such as methanol diffuses through the wall of its line into another line transporting the water based copolymer, thus avoiding any precipitation that would occur due to incompatibility of the copolymer with the alcohol. Finally, the alcohol compatible chemical should ideally be at least partially biodegradable.
U.S. Pat. No. 4,937,002 describes a method for inhibiting precipitation of barium sulfate and other insoluble sulfates in aqueous injection or produced fluids having a pH of 7 or less, and is most effective in aqueous fluids having a pH of about 4 to about 7. The aqueous fluid is dosed with 1 to 500 ppm of an interpolymer consisting essentially of about 25 to 90 mole % of an ethylenically polymerizable carboxylic acid and 10 to 75 mole % of at least one copolymerizable comonomer. Exemplified are interpolymers formed from (1) acrylic acid, maleic acid (maleic anhydride) and hydroxypropyl acrylate, (2) acrylic acid and mono-methyl maleate, and (3) acrylic acid and maleic acid (maleic anhydride). These interpolymers have molecular weights of from 500 to 10,000. Compatibility with alcohol, particularly methanol, is not described.